So I bought a Pro-ject Pre Box RS... (Valve suggestions?)

I think your tube pairs are probably very similar.  I think they both could have been made in the Amperex factory in Heerlen, Holland.  Here is a post I made in a similar thread. Check out the Phillips tube code pdf and if that doesn’t help let me know:

I think the Phillips/Amperex tubes that people are recommending are tubes made in the Amperex factory at Heerlen, Holland. Phillips sold these tubes with many different labels. Phillips owned many tube factories, Amperex, Siemens, Mullard, Valvo and many more, and tubes made in one factory were often labeled with another factory’s "brand." Your Phillips Miniwatts could have been made at Heerlen.

You can tell a Heerlen, Holland tube by the left facing right triangle that is the first symbol in the bottom line of the etched tube code. You can read about these codes here:

https://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf

Any tube you’re likely to come across these days would have the ’New’ Code, illustrated on page three, etched on the side of the tube.

Thanks tomcy6,
I'll check out the codes and see if I can translate them :-)

You have some. Try them.

The tube codes are easy, if you can read them. Sometimes they are faint or invisible.

Top line is three characters:

tube type, tube type, change code (model or version #)

Bottom line is three or four characters:

factory symbol, year (last digit), month (A - L), week of the month.

If the codes are legible, post them and we can decipher them.